TWI743291B - Thyrsitor thermal switch device and assembly method therefor - Google Patents

Abstract

A device may include a lead frame, where the lead frame includes a central portion, and a side pad, the side pad being laterally disposed with respect to the central portion. The device may further include a thyristor device, the thyristor device comprising a semiconductor die and further comprising a gate, wherein the thyristor device is disposed on a first side of the lead frame on the central portion. The device may also include a positive temperature coefficient (PTC) device electrically coupled to the gate of the thyristor device, wherein the PTC device is disposed on the side pad on the first side of the lead frame; and a thermal coupler having a first end connected to the thyristor device and a second end attached to the PTC device.

Description

Thermal switch element of thyristor and its assembling method

The embodiments are related to the field of surge protection components, and more specifically, are related to overvoltage protection components and resettable fuses.

The thyristor is widely used in alternating current (AC) power control applications. Like other semiconductor switches, the thyristor generates heat when it conducts current. Components or devices that include thyristor fluid often include other components for measuring or managing the heat generation caused by thyristor fluid, including heat sinks, cooling fans, or temperature sensing for monitoring the temperature of the thyristor body Device. If temperature control is not performed, the thyristor may enter a thermal runaway state, which may lead to catastrophic failure. In cost-sensitive applications, large heat sinks or cooling fans are not an acceptable solution, forcing designers to specify that the thyristor should operate at conditions well below its maximum operating rating to prevent heat-related failures.

In light of these and other considerations, this disclosure is provided.

Each exemplary embodiment relates to an improved protection element. In one embodiment, a component may include a lead frame, wherein the lead frame includes a central portion The side pads are divided into side pads, and the side pads are arranged laterally with respect to the central part. The element may further include a thyristor element that includes a semiconductor die and further includes a gate electrode, wherein the thyristor element is disposed on the first side of the lead frame on the central portion. The element may also include a positive temperature coefficient (PTC) element, the positive temperature coefficient element is electrically coupled to the gate of the thyristor element, wherein the positive temperature coefficient element is located on the lead frame The first side is disposed on the side pad; and may include a thermal coupler having a first end connected to the thyristor element and a second end attached to the positive temperature coefficient element .

In another embodiment, a method may include providing a lead frame having a center portion and side pads, wherein the side pads are disposed laterally with respect to the center portion. The method may further include attaching a thyristor element to the first side of the central portion of the lead frame, the thyristor element including a semiconductor die and further including a gate electrode. The method may also include: attaching a positive temperature coefficient (PTC) element to the side pad on the first side of the lead frame; and connecting the first end of a thermal coupler to the thyristor element, and The second end of the thermal coupler is connected to the positive temperature coefficient element, wherein the gate electrode of the thyristor element is electrically connected to the positive temperature coefficient element.

100, 202: components

102: lead frame

104: central part

106: side pad

112: The first main terminal lead

114: second main terminal lead

116: gate lead

122: positive temperature coefficient element

124: thyristor fluid element

126: main terminal contact clamp

127: The first main terminal electrode

128: Thermal coupler

129: upper surface

130: first end

132: second end

134: gate electrode

136: ceramic substrate

138: Heat sink

140: Solder

144, 204: Shell

150: first side

200: configuration form

400: Process flow

402, 404, 406, 408: Operation

MT1: The first main terminal

Fig. 1A presents an exploded perspective view of a component according to an embodiment of the present disclosure.

FIG. 1B presents a top plan view of the component in an assembled form according to an embodiment of the present disclosure.

FIG. 1C provides a circuit diagram of an implementation manner of the device shown in FIG. 1A.

Fig. 2A presents a top plan view of the arrangement of the components in the first assembly stage.

Fig. 2B presents a top plan view of the arrangement of the components in the second assembly stage.

Fig. 2C presents a top plan view of the arrangement of the components in the third assembly stage.

FIG. 3 illustrates an exemplary graph showing the characteristics of an exemplary positive temperature coefficient element.

Figure 4 shows a flowchart of an assembling device according to some embodiments of the present disclosure.

The embodiments of the present invention will now be explained more fully hereinafter with reference to the accompanying drawings in which exemplary embodiments are shown. The embodiments should not be regarded as limited to the embodiments described herein. More precisely, these embodiments are provided so that the content of the disclosure will be thorough and complete, and will fully convey the scope of the content of the disclosure to those skilled in the art. In the drawings, the same numbers refer to the same parts throughout.

In the following description and/or the scope of patent application, the terms "located on", "overlaid on", "set on", and "located on" can be used in the following description and the scope of patent application . "Located on", "Overly on", "Set on", and "On" can be used to indicate that two or more components are in direct physical contact with each other. In addition, the terms "on", "overly on", "on on", and "on on" can also mean that two or more components do not directly contact each other. Lift For example, "on" may mean that one component is above another component without contacting each other, and there may be another component or other components between the two components. In addition, the term "and/or" can mean "and", it can mean "or", it can mean "mutually exclusive OR", it can mean "one", it can mean "some, but not All, which can mean "neither..." and/or it can mean "both...", but the scope of the claimed subject matter is not limited in this respect.

In various embodiments, a mixing element is provided that includes a thyristor element (for example, a triode for alternating current (TRIAC)) and a positive temperature coefficient element that acts as a thermal switch. The device can be configured into a configuration that can be improved in design for easier assembly and better integration into the components to be protected.

The term "thyristor element" used herein can include a single thyristor, silicon controlled rectifier (SCR) or AC triode element. As is well known, the thyristor is related to the silicon controlled rectifier, where the silicon controlled rectifier is composed of a layered structure having an N-type semiconductor region or layer and a P-type semiconductor layer or region, for example, according to PNPN The four-layer configuration is formed in sequence. In the thyristor, the gate is connected to the inner layer of the four-layer element. Unlike a single thyristor that conducts current in only one direction, an AC triode can be regarded as a type of thyristor that can conduct current in two directions. The AC triode can be triggered by applying a positive or negative voltage to the gate. Once the AC triode is triggered, it will continue to conduct, even if the gate current is interrupted, until the main current drops below a certain level called the holding current.

The embodiments of the present invention provide an improvement to the known components by integrating a positive temperature coefficient (PTC) type component into a compact device to control the operation of the thyristor component. FIG. 1A shows an exploded perspective view of the device 100 according to an embodiment of the disclosure, and FIG. 1B shows a top plan view of the device 100 in an assembled form according to an embodiment of the disclosure. In addition, FIG. 1C provides a circuit diagram of an implementation manner of the device 100 shown in FIG. 1A. As shown in FIG. 1A, the component 100 includes a lead frame 102, wherein the lead frame 102 includes a central portion 104 and side pads 106, wherein the side pads 106 are arranged laterally relative to the central portion 104. The lead frame 102 may generally be composed of conductive materials, such as metals, including copper materials, such as pure copper or copper alloys. The lead frame 102 may also include a first main terminal lead 112, a second main terminal lead 114, and a gate lead 116, as shown in the figure. The second main terminal lead 114 may be connected to the central part 104. The element 100 may further include a thyristor element 124. As in the known thyristor element, the thyristor element 124 may be formed in a semiconductor die as a multilayer structure in which different layers have different doping polarities. The thyristor element 124 may be implemented as an AC triode, where the thyristor element 124 includes a gate electrode. As shown in FIG. 1A, after assembly, the thyristor element 124 is disposed on the first side 150 of the lead frame (the upper side of the lead frame as shown in FIG. 1A) on the central portion 104. In this way, the second main terminal lead 114 can be electrically connected to the thyristor element 124 via the second main terminal electrode (not shown in the figure) of the thyristor element 124 on the lower surface opposite to the upper surface 129.

As shown in FIG. 1A, the element 100 includes a positive temperature coefficient (PTC) element 122, which in various embodiments may be a polymer positive temperature coefficient element. Such The element may be able to change the resistivity in a narrow temperature range (for example, in the range of 10 degrees Celsius or 20 degrees Celsius) by about 10,000 times. As discussed further below, after assembly, the positive temperature coefficient element 122 may be electrically coupled to the gate of the thyristor element 124, and specifically may be disposed on the side pad 106 on the first side 150 of the lead frame 102. As further shown in FIG. 1A, the element 100 may include a thermal coupler 128, which after assembly has a first end 130 connected to the thyristor element 124 and a second end 132 attached to the positive temperature coefficient element 122 . The thermal coupler 128 may be a high thermal conductivity body, such as a copper arm, which provides a high thermal conductivity path between the thyristor element 124 and the positive temperature coefficient element 122. In this way, when the thyristor element 124 heats up during operation, the positive temperature coefficient element 122 can therefore quickly heat up to obtain a temperature close to the temperature of the thyristor element 124.

As further shown in FIG. 1A, the component 100 may include a main terminal contact clip 126 configured to contact the first main terminal electrode 127 without contacting the copper arm, that is, not touching the thermal coupler 128. The main terminal contact clip 126 can provide a conductive path between the first main terminal lead 112 and the first main terminal of the thyristor element 124 (see MT1 shown in FIG. 1C) after assembly. In this way, during the operation of the element 100, current can be conducted between the first main terminal lead 112 and the second main terminal lead 114 to the second main terminal lead 114 via the thyristor element 124. As described in detail below, during operation, the current between the two leads can be adjusted by the current supplied through the gate lead 116.

After assembly, the thermal coupler 128 can also be used as an electrical connection between the gate electrode 134 and the positive temperature coefficient element 122 disposed on the upper surface 129 of the thyristor element 124. In this way, during operation, the positive temperature coefficient element 122 is electrically connected in series between the gate lead 116 and the gate electrode 134. In this way, the positive temperature coefficient element 122 can be used as a current regulator of the gate current supplied to the thyristor element 124. For example, under medium current operating conditions where the current conducted by the thyristor element 124 is not too high, the temperature of the thyristor element 124 can be kept below the maximum junction temperature T _jmax defined in the art. Specifically, if the junction temperature T _j rises above T _jmax , the leakage current can be high enough to trigger the sensitive gate of the thyristor. The thyristor element will then lose the ability to remain in the blocking state, and current conduction will begin without the application of external gate current.

The value of T _jmax can be determined according to the specific AC triode or thyristor element known in the art. For example, in some examples, T _jmax may be 110°C, 120°C, 130°C, or 140°C, or 150°C. The embodiments are not limited to this context. The positive temperature coefficient element 122 may be designed to be used as a relatively low resistance element _{when the temperature is lower than T jmax.} Therefore, sufficient gate current can flow from the gate lead 116 to the gate electrode 134 through the circuit to achieve the target operation of the thyristor element 124. When the temperature approaches T _jmax or reaches T _jmax , the PTC element 122 can be designed to have _{a trip temperature close to T jmax} , where the PTC element 122 is used as a relatively high resistance element. In a specific embodiment, the positive temperature coefficient element 122 can be designed to have a trip temperature of 130°C, and the T _jmax of the AC triode used as the thyristor element 124 is 150°C. In this way, the current from the gate of the thyristor element 124 can be reduced, so that the current conducted by the thyristor element 124 is reduced, thereby further limiting the heat generation of the thyristor element 124. Such current limitation can prevent damage to the thyristor element 124 and surrounding components, which may otherwise occur in elements lacking the positive temperature coefficient element 122 under thermal runaway conditions. As further shown in FIG. 1A, the component 100 may include a heat sink 138 that provides a thermal connection between the lead frame 102 and an external heat sink. The device 100 may also include a ceramic substrate 136 which is connected to the heat sink 138 by solder 140 and provides electrical isolation between the lead frame 102 and the heat sink 138. The heat sink 138 is exposed to external conditions and is connected to an external heat sink (not shown in the figure), which may be the shell of the final product.

Turning to FIG. 1B, it shows an assembled view of a variant of the element 100, where the element 100 also includes a housing 144 not shown in FIG. 1A. As in the known elements, the housing 144 may be a solid molding material, and the housing 144 surrounds the other components described above. In operation, the element 100 can be conveniently coupled to any circuit or any group of elements or components to be adjusted in, for example, AC applications. FIG. 1C provides a circuit representation of an implementation of the device 100, where the device 100 includes an AC triode as the thyristor element 124. In this way, the current can be adjusted in two opposite directions via the AC triode by means of the positive temperature coefficient element 122.

FIG. 2A presents a top plan view of the configuration form 200 of the element 202 in the assembly stage, which may be referred to as the first assembly stage (rather than the start of assembly). In this example, the element 202 may be substantially the same as the element 100 described above. The configuration 200 includes a frame for accommodating a plurality of elements during assembly, wherein the singulation of the elements (see, for example, the singulated element shown in FIG. 1B) can be performed after the assembly is completed. In the assembly stage shown in FIG. 2A, the thyristor element 124 is attached to the central portion 104 of the lead frame 102, for example, by welding. The gate electrode 134 and the first main terminal electrode 127 are arranged at On the upper surface 129, it faces outward (upward) and does not directly electrically contact the central portion 104 for holding the thyristor element 124. In addition, the second main terminal electrode (not shown in the figure) located on the lower surface of the thyristor element 124 electrically contacts the central portion 104. In addition, the PTC element 124 is connected to the side pad 106 by welding, for example.

FIG. 2B presents a top plan view of the arrangement form 200 of the components in the second assembly stage. In this assembly stage, the thermal coupler 128 is in place for electrically connecting the PTC element 122 to the thyristor element 124 and thermally coupling the PTC element 122 to the thyristor element 124. The thermal coupler 128 may be welded to the positive temperature coefficient element 122, and may be in the form of a metal clip attached to the gate electrode 134, and may be attached to the gate electrode by welding or wire bonding. In addition, the first main terminal contact clip 126 is in place and can be welded to the first main terminal lead 112. The first main terminal contact clip 126 is configured to contact the first main terminal electrode 127 without contacting the thermal coupler 128 using solder connection, for example. In the illustrated embodiment, the first main terminal contact clip 126 has a C shape to provide a large surface area for coupling to the first main terminal electrode 127 without contacting the gate electrode 134. The first main terminal electrode 127 may also have other shapes. In addition, in the embodiment shown in FIG. 2B, the thermal coupler 128 may extend beyond the plane of the first main terminal contact clip 126 to extend above the first main terminal contact clip 126 without touching the first main terminal contact clip 126, as shown in the figure. The thermal coupler 128 can also have other shapes, such as the right-angled shape of the embodiment shown in FIG. 1A.

2C presents a top plan view of the configuration 200 of the element 202 in the third assembly stage, in which a given set of components used to form the final element is enclosed in a housing 204 (e.g., epoxy material). For example, the thyristor element and the corresponding positive The temperature coefficient element is enclosed in a given case together, and the gate lead 116, the first main terminal lead 112, and the second main terminal lead 114 extend out of the case 204. Subsequently, the configuration 200 can be singulated to form a group of individual elements as shown in FIG. 1B.

In some embodiments, the size of the positive temperature coefficient element 122 can be designed to fit on the side pad 106 in a manner that does not extend beyond the side pad 106. In some embodiments, the positive temperature coefficient element 122 may have a rectangular or square shape in the plan view of FIG. 2A, where the size of the positive temperature coefficient element is 60 mil x 60 mil or less than 60 mil x 60 mil. The embodiments are not limited to this context.

In a variation of the above embodiment, the electrical characteristics of the positive temperature coefficient element 122 can be customized according to the electrical characteristics of the thyristor element 124 to be protected. As an example, a given positive temperature coefficient element can be characterized by the trip temperature. The trip temperature corresponds to the temperature that separates the low temperature state (conduction state) from the high temperature state (high impedance state). In the low temperature state, the resistance is relatively low and rises relatively slowly as the temperature rises, while in the high temperature state, the resistance is relatively low. In the state, the resistance becomes relatively much higher and rises relatively quickly as the temperature rises. Figure 3 provides an exemplary graph showing the resistance of an exemplary 200 mil square PTC test wafer as a function of temperature, where the resistance is plotted on a logarithmic scale. In this example, the trip temperature can be designed to be approximately 125°C. Below this temperature, the resistance is below a few ohms and increases by only one order of magnitude in the range of 100°C between 25°C and 125°C. Above the trip temperature, the resistance increases by four orders of magnitude (10 ⁴ ) within a range of only 10°C. Therefore, when the current is conducted through the PTC chip under the initial "cold" condition where the temperature is lower than 125°C, and the temperature of the PTC chip subsequently rises and exceeds 125°C by only a few degrees, all other conditions are the same. , The current through the positive temperature coefficient wafer can be reduced by many orders of magnitude. These characteristics can be achieved by coupling the positive temperature coefficient chip shown in FIG. 3 to the above-mentioned thyristor element (such as an AC triode, wherein the AC triode has a range of, for example, 125°C to 145°C). Maximum junction temperature) to be effectively used. In this way, when the temperature of the AC triode exceeds 125°C, the temperature of the AC triode can be indirectly controlled by reducing the gate current supplied through the gate terminal and the positive temperature coefficient chip. This limitation prevents current/thermal runaway scenarios by limiting the duration of the maximum temperature experienced by the AC triode to the target maximum level (for example, T _jmax ) and the value of the maximum temperature. In this way, the control of the operation of the AC triode element is maintained. In addition, the existence of the positive temperature coefficient chip enables the AC triode element to be close to T _jmax or operate at T _jmax , which is an improvement on the operation of the previously known AC triode element. In the operation of the bulk component, the operating temperature can be limited to a much lower temperature to prevent thermal runaway and potential damage to the component.

As an illustrative example only, in the conduction state of the AC triode, when a gate current of 100 mA is required, the gate driver can apply up to 12 volts. This condition will result in a maximum impedance of 120 ohms. In the blocking state, a maximum of 20 volts can be applied and the gate current will be limited to less than 0.1 mA to maintain the AC triode in the off state at a temperature of 125°C. In this case, the required impedance is 200 kiloohms or higher. Such a resistance change of more than three orders of magnitude can be easily achieved by the 60 mil×60 mil positive temperature coefficient element configured according to the embodiment of the present invention. It should be noted that for 60 mil x 60 mil die, The impedance value shown in Figure 3 using a 200 mil x 200 mil positive temperature coefficient wafer is proportionally increased by approximately 11 times.

It should be noted that in order to improve the design of the element (for example, the element 100), the thermal coupling between the PTC element 122 and the thyristor element 124 may be taken into consideration. For example, the T _jmax or other design limit of the thyristor element may be 130°C. Under the operating conditions of the element 100 of the element structure, the thermal coupling between the positive temperature coefficient element 122 and the thyristor element 124 can make the positive temperature coefficient element disposed on the side pad 106 when the thyristor element reaches 130°C The temperature of 122 can reach 110°C. Therefore, the positive temperature coefficient element 122 can be configured to have a trip temperature in the range of 110°C, so that when the positive temperature coefficient element 122 exceeds 110°C (corresponding to when the temperature of the thyristor element 124 exceeds 130°C) Condition) trigger high impedance state.

FIG. 4 shows a process flow 400 according to an additional embodiment of the present disclosure. In block 402, a lead frame is provided, wherein the lead frame has a center portion and side pads, wherein the side pads are arranged laterally with respect to the center portion. In various embodiments, the lead frame may include three leads, one of which is connected to the central portion.

In block 404, a thyristor element (such as an AC triode) is attached to the first side of the center portion of the lead frame. The thyristor element may include a semiconductor die having a gate electrode. The gate may include a gate contact formed on the upper surface of the semiconductor die.

In block 406, the PTC element is attached to the side pads on the first side of the lead frame. The positive temperature coefficient element can be soldered to the side pads, for example. In block 408, the thermal coupler is connected to the thyristor element on the first end and to the positive temperature coefficient element on the second end. The thermal coupler can be used to electrically connect the thyristor element to the positive temperature coefficient element, while also providing high thermal conductivity between the positive temperature coefficient element and the thyristor element.

Although the embodiments of the present invention have been disclosed with reference to certain embodiments, many modifications, changes, and changes can be made to the embodiments without departing from the field and scope of the present disclosure. Therefore, the embodiments of the present invention are not limited to the described embodiments, but may have a full scope defined by the language of the following patent application scope and the equivalent scope thereof.

100: component

102: lead frame

104: central part

106: side pad

112: The first main terminal lead

114: second main terminal lead

116: gate lead

122: positive temperature coefficient element

124: thyristor fluid element

126: main terminal contact clamp

127: The first main terminal electrode

128: Thermal coupler

129: upper surface

130: first end

132: second end

134: gate electrode

136: ceramic substrate

138: Heat sink

140: Solder

150: first side

Claims (13)

A thyristor thermal switching element includes: a lead frame, the lead frame comprising: a central portion; side pads, the side pads are arranged laterally with respect to the central portion; a thyristor element, the thyristor element It includes a semiconductor die and further includes a gate electrode, wherein the thyristor element is disposed on the first side of the lead frame on the central portion; a positive temperature coefficient element is electrically coupled to all of the thyristor element The gate, wherein the positive temperature coefficient element is disposed on the side pad on the first side of the lead frame; and a thermal coupler having a first end connected to the thyristor element and an attachment Connected to the second end of the positive temperature coefficient element, wherein the thermal coupler includes a copper arm, and the copper arm electrically connects the gate electrode to the positive temperature coefficient element, wherein the thyristor element includes The upper surface includes a gate electrode and a first main terminal electrode, wherein the first main terminal electrode surrounds the gate electrode and is electrically isolated from the gate electrode. The thyristor thermal switch element according to the first item of the scope of patent application, wherein the lead frame includes a copper material. The thyristor thermal switching element as described in item 1 of the scope of patent application, including A main terminal contact clip is included, and the main terminal contact clip is configured to contact the first main terminal electrode without contacting the copper arm. According to the thyristor thermal switch element described in the first item of the patent application, the lead frame further includes: a first main terminal lead electrically coupled to the first main terminal electrode of the thyristor element; A terminal lead is electrically coupled to the second main terminal electrode of the thyristor on a lower surface opposite to the upper surface; and a gate lead is electrically coupled to the positive temperature coefficient element. The thyristor thermal switching element according to the fourth item of the scope of patent application, wherein the copper arm is connected to the first surface of the positive temperature coefficient element, and wherein the gate lead is connected to the positive temperature coefficient element A second surface, the second surface being opposite to the first surface. The thyristor thermal switch element according to the first item of the scope of patent application, wherein the thyristor element includes an AC triode. The thyristor thermal switch element according to the first item of the scope of patent application, wherein the positive temperature coefficient element includes a polymer positive temperature coefficient element. The thyristor thermal switch element described in the first item of the patent application, wherein the positive temperature coefficient element includes a trip temperature, wherein the thyristor element includes a maximum junction temperature, and wherein the maximum junction temperature exceeds the maximum junction temperature. The trip temperature is 20 degrees Celsius or less than 20 degrees Celsius. A method for assembling a thyristor thermal switch includes: A lead frame is provided, the lead frame includes: a central portion; and side pads, the side pads are arranged laterally with respect to the central portion; a thyristor element is attached to the central portion of the lead frame On the first side, the thyristor element includes a semiconductor die and further includes a gate electrode; a positive temperature coefficient element is attached to the side pad on the first side of the lead frame; and the first side of the thermal coupler One end is connected to the thyristor element and the second end of the thermal coupler is connected to the positive temperature coefficient element, wherein the gate electrode of the thyristor element is electrically connected to the positive temperature coefficient element The thermal coupler includes a copper arm electrically connecting the gate electrode to the positive temperature coefficient element; a gate electrode and a first main terminal electrode are provided on the upper surface of the thyristor element , Wherein the first main terminal electrode surrounds the gate electrode and is electrically isolated from the gate electrode; and a main terminal contact clip is attached to the first main terminal electrode so that the main terminal contact clip cannot Contact the copper arm or the gate electrode. The assembling method of the thyristor thermal switch described in item 9 of the scope of the patent application further includes: connecting the first main terminal lead to the main terminal contact clip; coupling the second main terminal lead to the upper surface The second main terminal contact of the thyristor element on the opposite lower surface; and Connect the gate lead to the positive temperature coefficient element. The assembling method of the thyristor thermal switch according to the tenth patent application, wherein the connecting the second end of the thermal coupler to the positive temperature coefficient element includes connecting the thermal coupler to The first surface of the positive temperature coefficient element, and wherein the connecting the gate lead to the positive temperature coefficient element includes connecting the gate lead to the second surface of the positive temperature coefficient element, so The second surface is opposite to the first surface. The assembling method of the thyristor thermal switch as described in item 9 of the scope of patent application, wherein the thyristor element includes an AC triode. The method for assembling a thyristor thermal switch as described in the scope of patent application, wherein the positive temperature coefficient element includes a polymer positive temperature coefficient element.

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